Simulated roots and host feeding enhance infection of subterranean insects by the entomopathogenic nematode Steinernema carpocapsae

Abstract

a b s t r a c tSteinernema carpocapsae can be effective against root-feeding insects despite its reputation as a sedentary ambusher. In pot experiments, using twigs as surrogate roots and pine weevil larvae as targets, we tested the hypothesis that roots serve as physical routeways and conduits of feeding-associated stimuli, thus enhancing the success of S. carpocapsae applied at the surface against subterranean hosts. Insect mortality was lowest (25%) in the absence of plant material, increased to 48% when twigs linked nematodes and insects, and further increased to 69% when the insects were allowed feed on the twigs. This is the first experimental support for the root-routeway hypothesis.

Host-seeking behavior of the Heterorhabditis amazonensis nematode in response to stimulant sources1

“…Even though this insect is not a soil pest, it was used as a model, indicating the changes that the feeding on plant roots can provide in the chemical components in the soil, since it triggered alterations in the nematode search. These data are consistent with those reported by Ennis et al (2010), who found that Picea sitchensis (Pinaceae), particularly when damaged by Hylobius abietis (Linnaeus) (Coleoptera: Curculionidae), form a chemical route for S. carpocapsae to find the host. According to Hiltpold & Turlings (2012), roots interfere in the dynamic of belowground herbivores, since they produce chemical exudates.…”

Organic soils promote the efficacy of entomopathogenic nematodes, with different foraging strategies, in the control of a major forest pest: A meta-analysis of field trial data

“…In peaty soils small un-degraded fibrous roots tend to persist to a greater depth in the rhizosphere than in mineral soils (Foth, 1978;Pitty, 1979). Ennis et al (2010) showed that roots can effectively act as routeways for the movement of S. carpocapsae IJs, so these small roots could contribute to the passage of EPN into the soil profile.…”

Over world distribution of Steinernematidae and Heterorhabditidae (Nematoda, Panagrolaimida et Rhabditida) entomopathogenic nematodes

“…Number of species in biogeographic regions WP EP NA AT AU NT OL Number of species The distribution of entomopathogenic nematodes depends on different abiotic and biotic factors: temperature [13,16], density, humidity [18] and chemical composition of substrate [3,14,15]; composition of phytocenosis [2,7]; climatic factors of a region; host finding strategy [4,8] and climatic preferences of nematodes [5], etc.…”